Circuit Card Assemblies (CCAs) are proliferate and found in every electronic device from the simplest toy to the most complex military system. CCAs are manufactured with heavy metals and toxic substances that can be expensive to manufacture as well as challenging to recycle. The need to repair these assemblies versus scrap and replace is becoming not only important from a sustainability perspective but also a cost perspective. Prior art Analog Signature Analysis based systems are not capable of verifying the parametric performance of CCAs. The testing and verification of a CCA is normally accomplished by testing the CCA in its next higher assembly, e.g. the next highest assembled system, or through the use of independent and cost prohibitive systems.
When tested at the assembly level, a successful test simply indicates the assembly is Ready-for-Issue (RFI) in the U.S. Navy and Department of Defense (DoD) agencies, or “Certified for Reuse” or “Tested OK” in commercial industry.
The primary goal of testing CCAs, whether automated or manually, is to identify the specific components on the CCA that are faulty to minimize the repair cost, maximize the speed of repair, and eliminate the need for repetitive testing. The scope of fault identification during any specific test is defined as an ambiguity group. An ambiguity group is typically a collection of faults which can be detected and isolated during a test. A more detailed definition is set forth below. Example: if the Safe-To-Turn-On (STTO) test fails, the ambiguity group is that the CCA as a whole and the specificity of failed components is unknown, i.e. the failure is very ambiguous and repair of the CCA is not feasible unless more detailed testing can be performed, such as by ASA.
The first step is parametric testing. Parametric testing of a CCA, in one example, is performed by connecting one or more stimulus instruments to “pins” on the edge connector and one or more measurement instruments to other “pins” on the edge connector. Connections other than edge connections can be used. Signals are applied and measurements taken. This level of testing validates whether the circuit that exists between each of the pins or other connections along with each of the plurality of components within that circuit are functioning properly. On a failure, the ambiguity group consists of every component in the circuit as well as the solder points and traces on the CCA that make up that circuit and can result in a fairly large ambiguity group. Repair following parametric testing may be feasible but may also result in more work and cost than is necessary.
To further isolate the root failure requires additional diagnostic testing such as using a guided probe (manually or automated). Manual interrogation or probing is performed by a human technician using hand-held meters and scopes and has several drawbacks, including accuracy, speed, and safety. Accuracy may be difficult during a manual probe due to the shrinking size of components and CCAs in general. This also leads to possible safety issues where an inadvertent short on a circuit can result is severe damage to the CCA and even harm to the technician. The ability to rapidly probe a CCA manually may also be difficult as the technician needs to find specific components in the circuit to perform the probe.
Automated guided probing offers the benefits of accuracy through consistent repeatable step-by-step operations controlled by software on a computer. This accuracy significantly reduces the likelihood and often eliminates the possibility of shorting a circuit and further damaging the CCA. Additionally, the automation ensures a thorough and rapid analysis of the CCA, Because of the accuracy of guided probing, guided probing also provides finer granularity in diagnostic capabilities over parametric diagnostics alone.
When additional isolation of probable fault is necessary beyond guided probing, the use of analog signature analysis (ASA) may also be performed on the CCA. ASA outputs a precision current-limited AC sine wave signal to a component and records the resulting current flow, voltage drop and any phase shift. The current flow causes a vertical trace deflection, while the voltage across the component causes a horizontal trace deflection. This resultant trace is called an analog signature. Signatures are stored for good CCAs and are used to compare against suspect CCAs.
The use of Parametric tests, active probing, and ASA with separate systems can be very time consuming, and the cost of having separate systems can be very high. This causes testing of CCAs to be expensive and time consuming. Often CCAs are not repaired or only partially tested as part of an assembly wherein component based failures cannot be detected reliably.
The present invention describes a system and computer program that enables a cost effective solution for the comprehensive testing (functional, parametric, and diagnostic) of CCAs. The combination of the technologies identified in this patent application will allow parametric testing to integrally work with analog signature analysis type systems such as the Huntron Tracker® ASA technology and Probing systems to RFI CCAs.
Additionally, the combination of the technologies will allow integrated automated active circuit probing for both signal injection and parametric measurement during test.